Method of tempering electric heater shells made of phenol-formaldehyde condensation product



S. FREEMAN April 114%, 193$.

METHOD OF TEMPERING ELECTRIC HEATER SHELLS MADE OF PHENOL FORMALDEHYDECONDENSATION PRODUCT Filed May 19, 1930 HNVEN l O ATTORN E15 PatentedApr. 14, 1936 UNITED STATES PATENT OFFICE Samuel Freeman, New York, N.Y.

Application May 19, 1930, Serial No. 453,595

1 Claim.

v My invention relates broadly to a method of tempering molded articlesof phenol-formaldehyde condensation resin, which are subject to hightemperatures during usage, as for instance 5 when they are used asshells for electric heaters, and in particular as a new and improvedsocket for an electric curling device.

One of the objects of my invention is to provide a new and improvedsocket for a device of this character, this socket being made of aresinous condensation product such as the phenol-formaldehyde syntheticresins.

Another object of my invention is to provide a new and improved methodof making such a socket.

Another object of my invention is to produce an improved socket whichcan be subjected to the relatively high temperature produced by theelectric heating coil commonly used in connection with hair curlingdevices, without blistering.

Other objects of my invention will be set forth in the followingdescription and drawing which v illustrate a preferred embodimentthereof, it being understood that the above general statement of theobjects of my invention is intended to merely generally explain the sameand not to limit it in any manner.

Fig. 1 is a rear elevation. Fig. 2 is a top view.

Fig. 3 is a side elevation.

Fig. 4 is a sectional view on the line 44 of Fig. 2.

Fig. 5 is a sectional view on the line 55 of Fig. 4.

Fig. 6 is a sectional View showing the parts separated.

Fig. '7 is a modified form.

The shell or socket I is preferably made of a phenol-formaldehydecondensation product which 4.0 is a well known synthetic resin. Theshell or socket I is provided with an insert or cap 2, having a lateralprojection 3a which is provided with two longitudinal perforationsthrough which line wires W can extend. The cap 2 has a metal shell 3connected thereto by a drive fit or other suitable means and the cap 2is also provided with an enlargement 2a at its lower or inner portion.This enlargement or flange 2a rests upon a shoulder which is provided inthe member I.

The metal shell 3 is provided with an outer covering 4 which is made ofmica or other suitable insulating materials, and an electric heatingcoil H is wound upon said insulating cover or sleeve 4.

Another covering 5 made of mica or like material surrounds the heatingcoil H, and the outer cover 5 is provided with a tightly wound layer Aof asbestos. The asbestos covering retains the coil H in position.Additional covering sheets 6 of mica or other insulating material canalso be 5 utilized.

The heating coil H is provided with terminals T to which the wires W areconnected.

In the modification shown in Fig. 7, the inner metal sleeve 3 isreplaced. by a metal sleeve 35 10 which projects above the cap 2.

As shown in Fig. 4, the metal sleeve 3 extends through the cap 2 and itrests upon a shoulder which is provided therefor in the member I.

The shell I and the cap 2 can be held together 15 by means of cement Cor by any other suitable means.

Experience has shown that in using devices of this character, the shellespecially if made by the usual hot molding process, will blister. This20 renders the device unsightly and in addition the blister is oftenaccompanied with a noise which frightens the person whose hair is beingcurled.

I have discovered that it is possible to temper said resin after it hasbeen completely molded by 25 the usual process. For this purpose, themolded piece (or pieces) of resin is subjected to a suitable heatingtreatment.

For example, the members I and 2 may be placed in a furnace where theycan be subjected 0 to a first heat treatment at C. for a period ofsixteen hours, and to a second heat treatment at C. for two hours. Thepieces of resinous material are subjected to the action of the hot airin the furnace in a uniform manner during 5 the tempering treatment.

A temperature higher than 130 C. may be utilized in the last heatingperiod of two hours. For example, temperatures of 0., 0., C. and C. maybe utilized. 40

The length of the shell and of the heating. coil should. be preferablysuch as to permit the tempered shell to radiate heat sufiiciently toprevent the temperature of the metal shell 3 from exceding 455 F. whenthe device is in use. 45

The insulation exterior to the asbestos can be eliminated if this isdesired. The device should be designed so that when it is in use itstemperature does not exceed the maximum temperature in the temperingtreatment. 50

The length and/or width of the shell can be suitably increased so as toprevent its temperature from exceeding the desired limit, when thedevice is in use.

While my invention has particular applica- 55 tion for use in connectionwith an electric hair curler, it is not necessarily to be restrictedthereto as it can be applied for other purposes where said resinousmaterial is subjected to a relative- 1y high temperature.

It is assumed in connection with this tempering process, that thesynthetic resin which is used for making the shell I and the cap 2consists substantially of the ordinary particles which are formed intothe desired shape, under suitable heat and pressure.

Attention is called to the fact, that this supplementary heat-treatmentof substantially pure phenol-formaldehyde condensation resin, pressed inhot molds, for the purpose of tempering the cooled and finishedproducts, is not identical with the so-called baking process, used inthe cold molding process to dehydrate the cold-pressed products and tofacilitate the setting or polymerization of the constituents. It alsohas nothing to do with the heat treatment of so-called cured phenolicmixtures, mostly in laminated form, in which the liquid resin is onlyused as a resinous binder for asbestos, wood pulp, silica magnesite,

etc., and forms a minor portion of the mixture, said heat treatmentafter molding being employed to improve the dielectric strength of themixture and generally being of longer duration and higher initialtemperature than applicant's tempering process.

I have shown a preferred embodiment of my invention, but it is clearthat numerous changes and omissions could be made without departing fromits spirit.

I claim:-

A method of tempering the shell of a heater which has an electricheating coil therein, in order to prevent said shell from blisteringwhen said shell is heated, said shell having been made by a hot-moldingprocess from a phenol-formaldehyde condensation product, which consistsin subjecting the finished shell to a supplemental heat treatment forabout sixteen hours at a temperature of about 85 (3., and then heatingsaid 20 shell for an additional period of about two hours at atemperature which is not less than about 130 C.

SAMUEL FREEMAN.

